| Attachment | Size |
|---|---|
| USBI-NABC24-Lori-Tunstall-Biochar-Cement.pdf | 1.51 MB |
The Feasibility of Biochar as a Cement Replacement to Reduce Concrete’s Carbon Footprint
Lori E. Tunstall, Ph.D.
Colorado School of Mines
In this presentation, we show that biochar-cement mortars have similar or improved 28-day strength compared to a control with no biochar (strengths ≥ 50 MPa).
We assess 16 distinct biochars for these mortars, with cement weight replacements of 10%. The biochars are made from softwood, hardwood, and agricultural feedstocks processed at temperatures ranging from 400 to 1100 °C using various pyrolysis techniques.
A subset of biochar-cement concretes were also assessed for permeability via water penetration depth measurements; the depth of water penetration decreases with increasing biochar content for each biochar assessed. Additionally, preliminary analysis indicates that biochar is compatible with fly ash as a cement replacement and can accelerate strength gains compared to mortars with only a fly ash-blended cement binder.
To successfully integrate biochar into cementitious composites we recommend the following: 1) mill the biochar; and 2) use biochar with high available sorption capacity, low O/C, and high soluble silicon content.
Finally, we demonstrate that we can produce a carbon negative biochar-cement mortar with strength parity to a traditional cement mortar and discuss the target biochar price to be competitive for use in the concrete industry.